1. Field of the Invention
The present invention relates to a semiconductor device used for an acceleration sensor, an angular velocity sensor, an electrostatic actuator or the like.
2. Description of the Background Art
In an inertial force sensor, an acceleration sensor, an angular velocity sensor, an electrostatic actuator or the like, conventionally, variation in static capacitance between a moving element and a stator in a case where the moving element and the stator are adjacently disposed, being spaced, and the moving element is moved has been detected as shown in, e.g., Japanese Patent Application Laid-Open Nos. 05-340961, 10-104265, and 05-142252.
In this case, as the moving element used is a semiconductor device having a silicon microstructure of triple-layered structure consisting of glass, silicon and glass, in which potentials of constituent elements are drawn out through holes in one of the glasses.
As to drawing of potentials of constituent elements made of silicon, conventionally, through holes are formed on one of the glasses and electrode pads are exposed in these through holes, to which wires are bonded.
Such a drawing structure with electrodes, however, needs a size of through hole large enough to accommodate a bonding tool (capillary) and disadvantageously has a limitation on reduction in chip size.
Further, in general, while a capacitance of the silicon microstructure is about 0.5 pF, the amount of variation in static capacitance in accordance with the inertial force, the acceleration or the like is about a tenth of the capacitance and this requires detection of very small static capacitance. On the other hand, when other substance approaches the silicon microstructure, an electric flux line of the capacitance in the silicon microstructure changes and a value of static capacitance disadvantageously changes regardless of the inertial force, the acceleration or the like. Furthermore, the same problem of variation in static capacitance is also caused by influence of electric charges such as static electricity or influence of disturbance such as radio wave hindrance. Therefore, there has been a possibility that it becomes hard to measure the inertial force, the acceleration or the like with high accuracy.